Abstract
PurposeTo compare treatment plans for interstitial high dose rate (HDR) liver brachytherapy with 192Ir calculated according to current-standard TG-43U1 protocol with model-based dose calculation following TG-186 protocol.MethodsWe retrospectively evaluated dose volume histogram (DVH) parameters for liver, organs at risk (OARs) and clinical target volumes (CTVs) of 20 patient cases diagnosed with hepatocellular carcinoma (HCC) or metastatic colorectal cancer (mCRC). Dose calculations on a homogeneous water geometry (TG-43U1 surrogate) and on a computed tomography (CT) based geometry (TG-186) were performed using Monte Carlo (MC) simulations. The CTs were segmented based on a combination of assigning TG-186 recommended tissues to fixed Hounsfield Unit (HU) ranges and using organ contours delineated by physicians. For the liver, V5Gy and V10Gy were analysed, and for OARs the dose to 1 cubic centimeter (D1cc). Target coverage was assessed by calculating V150, V100, V95 and V90 as well as D95 and D90. For every DVH parameter, median, minimum and maximum values of the deviations of TG-186 from TG-43U1 were analysed.ResultsTG-186-calculated dose was found to be on average lower than dose calculated with TG-43U1. The deviation of highest magnitude for liver parameters was -6.2% of the total liver volume. For OARs, the deviations were all smaller than or equal to -0.5 Gy. Target coverage deviations were as high as -1.5% of the total CTV volume and -3.5% of the prescribed dose.ConclusionsIn this study we found that TG-43U1 overestimates dose to liver tissue compared to TG-186. This finding may be of clinical importance for cases where dose to the whole liver is the limiting factor.
Highlights
Since the publication of the report of the American Association of Physicists in Medicine’s (AAPM) Task Group (TG) 186 [1], which advocates the use of modelbased dose calculation (MBDC) as replacement to the (2020) 15:60MBDC of current interest for 192Ir brachytherapy include collapsed-cone point kernel superposition [11,12,13], gridbased Boltzmann solvers [14, 15] as well as reference Monte Carlo (MC) simulation [16]
We report the comparison of Dw,w and Dw,m in the following subsections, divided into liver, Organ at risk (OAR) and clinical target volume (CTV) dose volume histogram (DVH) parameter analysis
Liver dose As an assessment of the influence of TG-186 on DVH parameters for the liver, we report Dw,w-calculated parameters as well as the absolute difference between Dw,m- and Dw,w-calculated parameters for Volume receiving at least 5 Gy (V5Gy) and Volume receiving at least 10 Gy (V10Gy) shown in Table 3 and Fig. 1a
Summary
Since the publication of the report of the American Association of Physicists in Medicine’s (AAPM) Task Group (TG) 186 [1], which advocates the use of modelbased dose calculation (MBDC) as replacement to the (2020) 15:60MBDC of current interest for 192Ir brachytherapy include collapsed-cone point kernel superposition [11,12,13], gridbased Boltzmann solvers [14, 15] as well as reference Monte Carlo (MC) simulation [16]. Since the publication of the report of the American Association of Physicists in Medicine’s (AAPM) Task Group (TG) 186 [1], which advocates the use of modelbased dose calculation (MBDC) as replacement to the (2020) 15:60. In the context of 192Ir high dose rate (HDR) brachytherapy, the use of MBDC is important for treatment sites in the vicinity of tissue/air or tissue/lung interfaces, and wherever variations of tissue density play an important role [1]. The treatment of liver malignancies by CT-guided HDR brachytherapy, where fluoroscopy-CT is employed for catheter insertion and three dimensional (3D) breath-hold CT for treatment planning, is associated with encouraging clinical results for liver metastases as well as hepatocellular carcinoma [18, 19]. At the hospital of the Ludwig-Maximilians-Universität München (LMU Munich), 196 patients were treated with interstitial brachytherapy for liver malignancies in 2018 , and coincidentally in 2019
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
